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Technique For Preventing Data Stored In A Memory Of Telephone System From Being Corrupted During Power Failure - Patent 5881128

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CLAIM OF PRIORITYThis application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. .sctn.119 from an application entitled Technique for Preventing Data Stored in a Memory of Telephone System from Being CorruptedDuring Power Failure earlier filed in the Korean Industrial Property Office on 12 Feb. 1996, and there duly assigned Serial No. 3315/1996 by that Office.BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to telephone systems and, more particularly, to a technique for preventing data stored in a memory of a telephone system from being corrupted during a power failure.2. Description of the Related ArtIn a telephone system, important data which must be stored in a memory even during a power failure is generally backed up by a battery. As a memory, a SRAM (static random access memory) which is easily available in the market is widely used.In an earlier circuit for storing data of a memory of a telephone system during a power failure, the memory receives an address, data, a read signal and a write signal from a processor. A chip enable terminal of the memory is connected to anoutput terminal of an OR gate. The OR gate has one terminal connected to a memory enable signal and has another terminal connected through an inverter to an output of a voltage sensing circuit. A decoder receives signals from the processor andgenerates the memory enable signal. In order to store important data even during a power failure, a power source is applied through an external battery to the inverter and to the OR gate and the decoder. During the power failure, the data stored in thememory as prevented for being overwritten and corrupted by disabling the chip enable terminal of the memory in response the output of the voltage sensing circuit.The following patents each disclose features in common with the present invention but do not teach or suggest a circuit for preventing data stored in the mem

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